Hawke's Bay principals are apprehensive ahead of National Standards data being made public next week.
Public Achievement Information will be published on the Ministry of Education website, Education Counts, next week despite huge opposition from the education sector.
Hawke's Bay Primary Principals Association vice-president and Te Mata School principal Mike Bain said there were fears that data would be used to unfairly compare schools.
"There is a strong feeling that we don't want people using that data for self-advocacy to sell their school and compare that to others," he said.
"I believe in healthy competition but there is anxiety around the trustworthiness of the data itself.
"There are a lot of apprehensions around what it could look like and what will it look like."
National Standards are assessment benchmarks for pupils in Years 1 to 8 that place achievement in reading, writing and mathematics at four levels: well below; below; at; above the national standard.
Education Minister Hekia Parata said the information would raise achievement by identifying children who were behind and helping parents and teachers focus on specific needs.
"Good quality data is absolutely essential if we are going to achieve a system-wise life and ensure all our learners leave school with the skills they need in modern society," she said.
However, opposition groups believe the data is flawed because the system has not been trialled, evaluated or moderated between schools and only showed a narrow and incomplete picture of student learning.
Data variations between schools were also a concern, as no specified reporting style was required by the ministry.
Vice-president of the education union, the New Zealand Education Institute, Frances Guy said yesterday the information was "ropey and misleading".
"Poor information will cause damage to schools and their communities," Mrs Guy said.
"Children are labelled as successes or failures to a one-size-fits-all measurement.
"Releasing bad data and allowing media to draw up league tables will create winner and loser schools."
Mr Bain said schools in Hawke's Bay had been inundated by media requesting copies of their data to publish.
"What we would absolutely hate to see is a headline that read 'Hawke's Bay's worst school' or something like that.
"Parents and the community have a right to know how their school is doing but I am certain that league tables are not the best way to do that," Mr Bain said.
"If it is only being presented in a table form there is so much more a school offers than pure academics."
Mr Bain feared a standardised national test could be on the cards.